Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07H—SUGARS; DERIVATIVES THEREOF; NUCLEOSIDES; NUCLEOTIDES; NUCLEIC ACIDS
  • C07H17/00—Compounds containing heterocyclic radicals directly attached to hetero atoms of saccharide radicals
  • C07H17/04—Heterocyclic radicals containing only oxygen as ring hetero atoms
  • C07H17/08—Hetero rings containing eight or more ring members, e.g. erythromycins
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
  • A61P31/00—Antiinfectives, i.e. antibiotics, antiseptics, chemotherapeutics
  • A61P31/04—Antibacterial agents

Definitions

• the present invention relates to a novel method of preparing novel chemical compounds having antibacterial activity, which are useful in the therapy of bacterial infections in mammals.
• the compounds made by the method of this invention are also themselves useful as antibacterial compounds. More specifically, the method of preparation of the present invention, and the method of use of the novel starting material for the preparation, relates to derivatives of the well-known macrolide antibiotic, erythromycin A, the compound of the structure:
• the invention relates to a method of making 9-deoxo-8a-aza-homoerythromycin A and its 8a-alkyl and hydroxy derivative compounds of the general structural formula:
• R is hydrogen hydroxy or 1-10 carbon alkyl and n is 0 or 1, and the pharmaceutically acceptable salts thereof.
• the nomoenclature used herein follows from the nomenclature used in the description of macrolides found in U.S. Pat. No. 4,328,334.
• the compounds of formula (II) are obtained by reacting novel 8a-aza-8a-homoerythromycin cyclic iminoethers of the formula with a suitable reducing agent to obtain a compound of the formula IV is then alkylated to obtain compounds of formula II.
• R is as defined above for alkyl substituents.
• the compounds of formula II can be prepared readily according to the following detailed descriptions and accompanying examples or modifications thereof using readily available starting materials, reagents and conventional synthesis procedures. The overall process is illustrated in the following Flow Sheet wherein alkylation steps are explicitly described below.
• (9Z)-9-Deoxo-9-hydroximinoerythromycin A is used as the starting compound in the synthesis of 8a-aza-8a-homoerythromycin cyclic iminoethers.
• This compound is novel and is obtained by an isomerization of (9E)-9-Deoxo-9-hydroxyiminoerythromycin A.
• the (E) geometric isomer of the formula is reacted with a suitable base in the presence of a protic or an aprotic solvent.
• the base is an alkali metal hydroxide, and most preferably is lithium hydroxide.
• the solvent is preferably an alcohol and most preferably is ethanol.
• the workup performed on the anions includes protonation of the oxime anions to give the neutral oxime product mixture from which the desired Z-isomer (VI) is isolated by crystallization or by chromatography followed by crystallization.
• the relative amounts of E and Z oxime anions (and neutral oximes after the workup) in the equilibrium mixture can be controlled and depends on a number of factors. These include (a) the strength and quantity of the base reagent, (b) the size and polarity of the counterion + M, (c) the reaction solvent, and (d) the reaction temperature.
• Suitable bases include hydroxides, alkoxides, carbonates, metalamides, amines and metalhydrides.
• the isomerization to obtain the (Z) isomer is carried out at a concentration of 1-25% w/v of E-oxime to solvent, and most preferably at 10% w/v.
• the amount of base used is preferably 1.0-10.0 molar equivalents based on the amount of starting E-oxime, more preferably 1.0-3.0 molar equivalents, and most preferably 2.0 molar equivalents.
• the reaction is generally run at a temperature of from 0°C to 80°C, and more preferably at 22-25°C.
• the reaction can be allowed to run for 0.5 hours - 20 days, but most preferably is carried out over 20-24 hours.
• the mechanism of the rearrangement involves initial conversion of the oxime hydroxyl group to a leaving group which is then lost with concomitant migration of the oxime carbon substituent that is situated anti to the leaving group.
• the intermediate nitrilium cation thus formed usually reacts with water to afford the amide product.
• the nitrillium intermediate can also be trapped by other suitable nucleophiles thereby leading to imino products such as imidates and amidines.
• the Beckmann rearrangement has been accomplished under a variety of acidic, neutral and basic conditions.
• acidic reagents that promote the transformation include concentrated sulfuric acid, polyphosphoric acid, thionyl chloride, phosphorous pentachloride, sulfur dioxide, and formic acid. These reagents are generally not applicable to the rearrangement of oxime (VI) due to the sensitivity of the macrolide molecule, and especially the cladinose sugar residue, to acidic conditions.
• Efficient Beckmann rearrangement also occurs by heating the oxime with silica gel in xylene or under mildly basic conditions by heating the oxime in hexamethylphosphoramide. These conditions are not particularly valuable for the conversion of (VI) to products (VII), (VIII) and (IX) due to competing isomerization of the oxime function under the reaction conditions.
• a preferred method for effecting the Beckmann rearrangement involves initial O-acylation of the oxime group with an alkylsulfonyl halide, arylsulfonyl halide or arylsulfonic anhydride.
• the intermediate oxime sulfonate thus formed can be isolated or, as more commonly practiced, converted in situ to the rearranged products.
• the acylation and rearrangement reactions are generally performed in the presence of an organic or inorganic base. This method is particularly valuable for the conversion of oxime (VI) to the rearranged products (VII), (VIII), and (IX).
• Preferred acylating reagents for effecting the rearrangement of oxime (VI) include methanesulfonyl chloride, benzenesulfonyl chloride, 4-acetamidobenzenesulfonyl chloride, p-toluenesulfonyl chloride, benzenesulfonic anhydride, and p-toluenesulfonic anhydride.
• the reaction is carried out in the presence of an inorganic base such as sodium bicarbonate or potassium carbonate, or in the presence of an organic base such as pyridine, 4-dimethylaminopyridine, triethylamine, or N,N-disopropylethylamine.
• Suitable solvents include aqueous mixtures such as aqueous acetone or aqueous dioxane and organic solvents such as dichloromethane, chloroform, ethyl acetate, diethyl ether, tetrahydrofuran, toluene, acetonitrile, and pyridine: Mixtures of organic solvents, especially those containing pyridine, are highly useful.
• the reaction is generally performed using 1-3 molar equivalents of the acylating agent and one or more molar equivalents of base at a raction temperature of -20°C to 50°C. Pyridine is often used as both solvent and base.
• the distribution of products resulting from Beckmann rearrangement of oxime (VI) depends on the particular reaction conditions employed. For example, when the rearrangement is effected with p-toluenesulfonyl chloride and sodium bicarbonate in aqueous acetone, the major products are the lactam (VII) and the cyclic 6,9-bridged iminoether (VIII). When the reaction is conducted under anhydrous conditions such as p-toluenesulfonyl chloride in pyridine, the major products are the cyclic 6,9-bridged and 9,12-bridged iminoethers (VIII) and (IX).
• the ratio of products (VIII) and (IX) is also effected by the addition of cosolvents, by temperature, and by the initial oxime concentration. In general, increasing the proportion of pyridine as solvent, increasing the reaction temperature, and decreasing the initial oxime concentration all favor the formation of the 9,12-product (IX) over that of the 6,9-product (VIII).
• a particularly preferred method for effecting the Beckmann rearrangement of oxime (VI) involves the addition of a solution of 2.5 molar ezuivalents of p-toluenesulfonyl chloride in diethyl ether to a solution of the oxime in pyridine at 0-5°C. Oxime O-sulfonylation and subsequent rearrangement occur udner the reaction conditions to afford a 1:3 mixture of iminoether products (VIII) and (IX).
• the products of the Beckmann rearrangement of oxime (VI) are conveniently purified by chromatographic methods.
• the lactam (VII) is easily separated from iminoether (VIII) using column chromatography on silica gel or by reverse phase, high-pressure liquid chromatography.
• products (VIII) and (IX) can also be separated by chromatographic methods, and the (IX) thus obtained can be further purified by crystallization.
• Compounds (VIII) and (IX) can be viewed as cyclic imidates (or imidic acid esters) of the macrocyclic lactam (VII).
• the imidates are formally, derived from the compound (VII) by transannular addition of the hydroxy groups at positions 6 and 12 to the lactam carbonyl group, followed by elimination of water.
• imidates (VIII) and (IX) most likely arise by intramolecular interception of the Beckmann rearrangement nitrilium intermediate with the 6- and 12-hydroxy groups.
• the second structure (IX) has the imino nitrogen atom exocyclic to a 5-membered ring containing the oxygen atom thereby giving rise to a 2-iminotetrahydrofuran system.
• a method of choice for reducing the macrocyclic imidates (VIII) and (IX) to the amine (IV) uses a complex metal hydride in an appropriate solvent system.
• Suitable hydride reagents include lithium aluminum hydride, sodium borohydride, sodium cyanoborohydride, and diisobutyl aluminum hydride.
• Both lithium aluminum hydride and diisopbutyl aluminum require the use of anhydrous solvents such as benzene, toluene, diethyl ether, tetrahydrofuran and dimethoxyethane, whereas sodium borohydride and sodium cyanoborohydride can be used in the presence of water or in alcoholic solvents such as methanol, ethanol, isopropanol, and ethylene glycol.
• sodium cyanoborohydride is used the reaction medium is usually acidified by addition of aqueous acid (pH ⁇ 3) or acetic acid. The reaction is generally accomplished by treating the imidate with 1-5 molar equivalents of reductant for 1-20 hours at a temperature ranging from -20°C to 50°C.
• Ethylene glycol serves the dual purposes of activating the borohydride agent and of breaking up borate ester complexes of the amine product.
• a particularly preferred method for reducing imidates (VIII) and (IX) to the amine (IV) employs 2-3 molar equivalents of sodium borohydride in methanol or ethylene glycol at a temperature of 0°C to 25°C.
• a second method of choice for effecting the reduction of imidates (VIII) and (IX) to the amine (IV) is catalytic hydrogenation at high pressure.
• the reaction is usually accomplished by shaking a mixture of imidate and catalyst in a suitable solvent such as methanol, ethanol, aqueous dioxane or acetic acid at a hydrogen pressure of 1000-3000 psi for 2-20 hours at ambient temperature.
• Suitable catalysts include noble metals and their oxidized forms such as platinum on carbon, platinum oxide (Adams' catalyst), palladium on carbon, palladium hydroxide on carbon (Pearlman's catalyst) and rhodium on carbon.
• An especially preferred method for reducing imidate (IX) uses nearly an equivalent weight of platinum oxide catalyst in acetic acid at 2000 psi hydrogen for 18-20 hours at room temperature.
• Secondary amines such as (IV) can be reductively methylated to tertiary amines using formaldehyde in the presence of a reducing agent.
• Suitable reductants for this reaction include hydrogen in the presence of a noble metal catalyst, Raney nickel, sodium borohydride, sodium cyanoborohydride, and formic acid.
• the reaction can be conducted in a number of organic solvents, for example methanol, ethanol, acetonitrile, chloroform, tetrahydrofuran or dioxane, with or without the presence of added water.
• organic solvents for example methanol, ethanol, acetonitrile, chloroform, tetrahydrofuran or dioxane, with or without the presence of added water.
• Eschweiler-Clarke method involves the reaction of the amine with formaldehyde in the presence of formic acid.
• the methylation of compound (IV) can also be accomplished using a three-step procedure (see G. M. Bright, et al.,J. Antibiotics, 41, 1029 (1988) and U. S. Patent No. 4,474,768) in which (IV) is first oxidized to the N-hydroxide N ′-oxide intermediate (XI), then treated with a methylating agent to afford the intermediate product (XII), and finally deoxygenated to the desired product.
• the N ′ -oxygen serves as a temporary protecting group to prevent quaternization at the desosamine dimethylamino group.
• the oxidation step is conducted in an inert solvent using hydrogen peroxide or a peracid such as peracetic acid or 3-chloroperoxybenzoic acid as the oxidant.
• Suitable solvents for the reaction include dichloromethane, chloroform, tetrahydrofuran, dioxane, methanol, ethanol and acetic acid.
• a water miscible solvent such as methanol or acetic acid is used with the water-soluble oxidants hydrogen peroxide and peracetic acid
• an anhydrous solvent such as dichloremethane or tetrahydrofuran is used with 3-chloroperoxybenzoic acid.
• the reaction is usually accomplished with an excess of oxidant (2-40 molar equivalents) at a temperature of from 0°C to 50°C for up to 24 hours.
• a particularly preferred embodiment employs excess 30% aqueous hydrogen peroxide as oxidant in methanol solvent at room temperature for 18-20 hours.
• N-hydroxy-N ′-oxide intermediate (XI) is accomplished by treating the N-hydroxy-N ′-oxide intermediate (XI) with a methylating agent in an inert solvent in the presence of an acid acceptor.
• An inert solvent is defined as one that will not react with the methylating reagent under the reaction conditions.
• Suitable solvents include but are not limited to dichloromethane, chloroform, tetrahydrofuran, dimethoxyethane, dimethylsulfoxide, and toluene.
• methylating agents that are known to effect alkylation at nitrogen, methyl iodide, methyl bromide, dimethyl sulfate and methyl trifluoromethanesulfonate are well suited for the present application.
• the acid acceptor component which serves to neutralize the acid formed on reaction of the methylating agent with the ring nitrogen atom, can be an inorganic base such as an alkali metal hydroxide or carbonate, or a hindered amine base.
• suitable acid acceptors are sodium bicarbonate, potassium carbonate, potassium hydroxide, and 2,6-lutidine.
• the methylation reaction is generally accomplished using a large excess (10-75 molar equivalents) of both the methylating agent and the acid acceptor at a temperature of from 0°C-80°C for 1-20 hours.
• a preferred method involves stirring compound (XI) with approximately 40 molar equivalents of methyl iodide and 70 molar equivalents of anhydrous potassium carbonate in dichloromethane at room temperature.
• the final step of the sequence, the deoxygenation reaction of (XII) to provide (X), is readily accomplished by catalytic hydrogenation.
• the hydrogenation reaction is carried out at a temperature of 18°C to 25°C and at hydrogen pressures of from 15 psi to 2000 psi in an inert solvent.
• Suitable catalysts are noble metals and their oxides such as palladium on carbon, palladium hydroxide on carbon, platinum oxide, platinum on carbon, and rhodium on carbon.
• Representative inert solvents for the catalytic reduction are methanol, ethanol, tetrahydrofuran, dioxane, acetic acid and mixtures thereof.
• a typical catalytic reduction procedure uses ethanol as solvent, a hydrogen pressure or 45 psi, and 10% palladium on carbon as catalyst at a substrate to catalyst ratio of 1:1 to 1:2.
• the reductive deoxygenation of (XII) to (X) can also be accomplished with a number of chemical reductants.
• Representative reagents of this type include metal hydrides such as sodium borohydride or sodium cyanoborohydride, zinc in acetic acid, and triphenylphosphine.
• compositions of formula (II) are basic and therefore will form acid-addition salts.
• Pharmaceutically acceptable acid addition salts will be non-toxic salts which can generally be prepared by methods well known to those of ordinary skill in the art.
• the compounds of formula (II) are combined with a stoichiometric amound of an appropriate acid in an inert solvent, and then the salt is recovered by solvent evaporation or by filtration if the salt precipitates spontaneously, or by precipitation using a co-solvent or a non-polar co-solvent followed by filtration.
• Representative salts include the following salts:
• the compounds of formula (II) can be administered in such oral dosage forms as tablets, capsules, pills, powders, granules, elixirs, tinctures, suspensions, syrups and emulsions. Likewise, they may also be administered in intravenous, intraperitoneal, subcutaneous or intramuscular form, all using forms well known-to those.of ordinary skill in the pharmaceutical arts. In general, the preferred form of administration is oral. An effective but non-toxic amount of the compound can be employed as a mammalian antibiotic.
• the dosage regimen utilizing the compounds of formula (II) is selected in accordance with a variety of factors including type, species, age, weight, sex and medical condition of the patient; the severity of the condition to be treated; the route of administration; the renal and hepatic function of the patient; and the particular compound or salt thereof employed.
• An ordinarily skilled physician or veterinarian can readily determine and prescribe the effective amount of the drug required to prevent, counter or arrest the progress of the condition.
• Dosages of the compounds of formula (II), when used for the indicated effects, will range between about 0.2 mg per kg of body weight per day (mg/kg/day) to about 120 mg/kg/day and preferably 14-28 mg/kg/day.
• the compound may be administered in a single daily dose, or the total daily dosage may be administered in divide doses of two, three or four times daily.
• the compounds of formula (II) can be administered in topical,otic or ophthalmic form via use of suitable vehicles.
• carrier suitable pharmaceutical diluents, excipients or carriers (collectivity referred to herein as "carrier” materials) suitably selected with respect to the intended form of administration, that is, oral tablets, capsules, elixirs, syrups, and the like, and consistent with conventional pharmaceutical practices.
• the active drug component can be combined with an oral, non-toxic, pharmaceutically acceptable, inert carrier such as lactose, starch, sucrose, glucose, methyl cellulose, magnesium stearate, dicalcium phosphate, calcium sulfate, mannitol, sorbitol, and the like; for oral administration in liquid form, the oral drug components can be combined with any oral, non-toxic, pharmaceutically acceptable inert carrier such as ethanol, glycerol, water, and the like. Moreover, when desired or necessary, suitable binders, lubricants, disintegrating agents and coloring agents can also be incorporated into the mixture.
• suitable binders, lubricants, disintegrating agents and coloring agents can also be incorporated into the mixture.
• Suitable binders include starch, gelatin, natural sugars such as glucose or beta-lactose, corn sweeteners, natural and synthetic gums such as acacia, tragacanth or sodium alginate, carboxymethylcellulose, polyethylene glycol, waxes, and the like.
• Disintegrators include, without limitation, starch, methyl cellulose, agar, entonite, xanthan gum, and the like.
• the compounds of formula (II) can also be administered in the form of liposome delivery systems, such as small unilamellar vesicles, large unilamelar vesicles and multilamellar vesicles.
• Liposomes can be formed from a variety of phospholipids, such as cholesterol, stearylamine or phosphatidylcholines.
• the compounds of formula (II) may also be coupled with soluble polymers as targetable drug carriers.
• soluble polymers can include polyvinylpyrrolidone, pyran copolymer, polyhydroxypropylmethacrylamide phenyl, polyhydroxyethylaspartamidephenol, or polyethyleneoxide-polylysine substituted with palmitoyl residues.
• the compound of formula (II) may be coupled to a class of biodegradable polymers useful in achieving controlled release of a drug, for example, polylactic acid, polyglycolic acid, copolymers of polylactic and polyglycolic acid, polyepsilon caprolactone, polyhydroxy butyric acid, polyorthoesters, polyacetals, polydihydropyrans, polycyanoacrylates and cross-linked or amphipathic block copolymers of hydrogels.
• a drug for example, polylactic acid, polyglycolic acid, copolymers of polylactic and polyglycolic acid, polyepsilon caprolactone, polyhydroxy butyric acid, polyorthoesters, polyacetals, polydihydropyrans, polycyanoacrylates and cross-linked or amphipathic block copolymers of hydrogels.
• erythromycin A 100 g, ca. 95% pure, 0.129 mol, available from Aldrich Chemical Company, Inc., Milwaukee, Wisconsin
• pyridine 500 mL
• the resulting mixture was stirred at room temperature for 27 hrs., and then concentrated under vacuum at ca. 40°C.
• the semi-solid residue was kept under high vacuum overnight, then stirred with ethanol (600 mL) for 15 minutes and filtered. The collected solids were washed with hot (50°C) ethanol. The combined filtrate and washing was evaporated under vacuum to a pale blue foam.
• the crude oxime hydrochloride was suspended in 5% aqueous sodium bicarbonate (1000 mL) and methylene chloride (1000 mL), and the mixture was stirred while the pH was adjusted to 9.5 by addition of 5N aqueous sodium hydroxide. The layers were separated and the aqueous portion was extracted with ethyl acetate (500 mL) and ethyl ether (500 mL). The combined organic layer and extracts were dried over sodium sulfate, filtered, and evaporated under vacuum to a white solid (92.3 g). The solid was dissolved in hot ethyl acetate (250 mL), and the solution diluted with hot hexanes (400 mL) and left overnight in a refrigerator.
• the crude oxime mixture was dissolved in methylene chloride (220 mL) and stirred for 1 hour at room temperature to give a filterable, white solid (18.7 g).
• This material was dissolved in ethyl acetate (100 mL), diluted with nitromethane (100 mL), and 50 mL of solvent was evaporated under vacuum. Additional nitromethane (50 mL) was added and 80 mL of solvent was evaporated under vacuum. The solution was seeded with the (9Z)-isomer and stirred at room temperature for 3 hours.
• the product consisted of a 26:74 mixture of (9E)-9-deoxo-9-hydroxyimino-erythromycin A and (9Z)-9-deoxo-9-hydroxyimino-erythromycin A as determined by 1 H NMR spectroscopy.
• the above mixture was purified by preparative layer chromatography (two 0.1 mm x 20 x 20 cm Analtech silica gel GF plates, developing and eluting with 60:10:1 dichloromethane-methanol-concentrated ammonium hydroxide) to afford 8a-aza-8a-homoerythromycin A (95 mg, 48% yield) and 9-deoxo-6-deoxy-6, 9-epoxy-8a, 9-didehydro-8a-8aza-8a-homoerythromycin (33 mg, 17% yield).
• the aqueous residue was diluted with water (40 mL) and dichloromethane (60 mL) and stirred while the pH was adjusted to 5.5 with dilute hydrochloric acid.
• the aqueous layer was separated, washed with dichloromethane (60 mL), layered with dichloromethane (60 mL), and stirred while the pH was brought to 9 with dilute aqueous sodium hydroxide.
• the layers were separated and the aqueous portion extracted with more dichloromethane (2 x 50 mL).
• Benezenesulfonyl chloride (0.107 mL, 0.84 mmol) was added by syringe to an ice-cold solution of (9Z)-9-deoxo-9-hydroxyiminoerythromycin A (250 mg, 0.33 mmol) in pyridine (2.0 mL). The resulting solution was stirred at 0-5°C for 75 minutes, then processed as described above to afford a yellow solid (240 mg).
• This material was shown by 1 H NMR spectroscopy to be a 31 :69 mixture of 9-deoxo-6-deoxy-6,9-epoxy- and 9-deoxo-12-deoxy-9,12-epoxy-8a,9-didehydro-8a-aza-8a-homoerythromycin A.
• Methanesulfonyl chloride (0.065 mL, 0.84 mmol) was added by syringe to an ice-cold solution of (9Z)-9-deoxo-9-hydroxyiminoerythromycin A (250 mg, 0.33 mmol) in pyridine (2.0 mL). The resulting solution was stirred at 0-5°C for 2 hours, then processed as described above to afford an off-white solid (246 mg).
• This material was shown by 1 H NMR spectroscopy to be a 25:70:5 mixture of 9-deoxo-6-deoxy-6,9-epoxy-8a,9-didehydro-8a-aza-8a-homoerythromycin A, 9-deoxo-12-deoxy-9,12-epoxy-8a,9-didehydro-8a-aza-8a-homoerythromycin A, and 9-deoxy-12-deoxy-9,12-epoxy-4 ⁇ -O-methanesulfonyl-8a,9-didehydro-8a-aza-8a-homoerythromycin A.
• This material was shown by 1 H NMR spectroscopy to be a 88:12 mixture of 9-deoxo-6-deoxy-6,9-epoxy-8a,9-didehydro-8a-aza-8a-homoerythromycin A and 9-deoxo-12-deoxy-9,12-epoxy-8a,9-didehydro-8a-aza-8a-homoerythromycin A.
• a sample (4.0 g) of the crude product mixture obtained as described in method 1 was dissolved in 60:10:1 dichloromethane-methane-conc. aqueous ammonium hydroxide (6 mL) and the solution was loaded onto a column of EM silica gel 60 (4.5 x 18 cm, 230-400 mesh, wet packed under 60:10:1 dichlormethane-methanol-conc. ammonium hydroxide). The column was eluted with 60:10:1 dichloromethane-methanol-conc. aqueous ammonium hydroxide.
• the solution was diluted with water (50 mL), acidified to pH 2 with 2N hydrochloric acid, and stirred at room temperature for 10 minutes.
• the solution was diluted with water (150 mL) and dichloromethane (200 mL) and stirred vigorously while the pH was brought to 6.5 by addition of 5N sodium hydroxide.
• the dichloromethane layer was discarded and the aqueous phase layered with resh dichloromethane, stirred rapidly and basified to pH 9.5 with 5N sodium hydroxide.
• the layers were separated and the aqueous portion extracted with more dichloromethane (2 x 100 mL).
• the combined pH 9.5 dichloromethane extracts were dried over magnesium sulfate, filtered and evaporated under reduced pressure to a foam (15.4 g).
• the mother liquors and washings were evaporated under vacuum to a solid residue.
• the solid as suspended in water (50 mL), acidified to pH 2, and stirred at room temperature for 30 minutes.
• the mixture was diluted with water (50 mL) and dichloromethane (100 mL), then stirred vigorously while adjusting the pH to 6.5.
• the dichloromethane layer was discarded and replaced with fresh dichloromethane (100 mL).
• the mixture was stirred while the pH was adjusted to 9.5.
• the layers were separated and the aqueous phase was extracted with more dichloromethane (2 x 100 mL).
• the combined basic extracts were dried with magnesium sulfate, filtered and evaporated under vacuum to a foam (6.2 g).
• reaction mixture was stirred at 0-5°C for 1.5 hours, then warmed to room temperature and stirred at room temperature overnight.
• the reaction mixture was diluted with water (50 mL) and dichloromethane (25 mL), stirred vigorously, and the phases separated. The aqueous portion was extracted with more dichloromethane (4 x 25 mL). The combined organic extracts were washed with brine (50 mL), dried over magnesium sulfate, filtered and evaporated under reduced pressure to a foam (4.0 g).
• the foam was purified by preparative thin-layer chromatography (Analtech 0.1 mm x 20 x 20 cm basic alumina plate, developing and eluting with 5% methanol in dichloromethane) to give the title compound as a white foam (42 mg).
• step 1 A portion of the product from step 1 (150 mg, 0.196 mmol) was dissolved in dichloromethane (3 mL) and the solution was treated with powdered, anhydrous potassium carbonate (2.0 g, 14.5 mmol) and methyl iodide (0.5 mL, 8.0 mmol). The mixture was stirred at room temperature and under a nitrogen atmosphere for 3.5 hours. The mixture was filtered and the solids washed with dichloromethane (5 mL). Water (3 mL) was added to the combined filtrate and washings and mixture was stirred vigorously while the pH was brought to 11 with 1N sodium hydroxide .
• the dichloromethane phase was dried with magnesium sulfate, filtered and evaporated under reduced pressure to afford a mixture of 9-deoxo-8a-methyl-8a-homoerythromycin A 3′-N-oxide and 9-deoxo-8a-methyl-8a-homoerythromycin A 8a, 3′-N-bisoxide (136 mg) as a foam.
• the crude product was dissolved in ethanol (6 mL), treated with 10% palladium on carbon (240 mg), and hydrogenated on a Parr shaker for 75 minutes at 45 psi. The mixture was filtered and the filtrate was evaporated under vacuum. The residue in dichloromethane (20 mL) was washed with saturated aqueous potassium carbonate, dried with magnesium sulfate, filtered, and evaporated under reduced pressure to provide 9-deoxo-8a-methyl-8a-homoerythromycin A (107 mg) as a foam.
• the antibacterial activities of compounds (IV), (X) against a panel of aerobic Gram positive and negative bacteria is shown in the following Table.
• the assay employs a liquid turbidimetric microtiter method for the determination of the minimum inhibitory concentration (MIC) in brain heart infusion broth.
• the MIC endpoint in mcg/ml is defined as the lowest concentration of test compound that completely inhibits the growth (absence of turbidity) of bacteria.
• the MIC is generally not an absolute value but rather a concentration range that falls within a two-fold dilution limit. Generally twelve two-fold dilutions of the test compound are employed with the initial concentration set at 128 mcg/ml.
• the compounds of formula (II) are useful as an antibacterial agents both in vitro and in vivo , and their spectrum of activity is similar to that of erythromycin A. Consequently, they can be used for the same purposes, and, in the same manner, as erythromycin A.
• the antibacterial compounds of formula II and salts thereof exhibit in vitro activity against a variety of Gram-positive microorganisms, e.g. Staphylococcus aureaus Streptococcus pyogenes , and against certain Gram-negative microorganisms such as those of spherical or ellipsoidal shape (cocci). Their activity is readily demonstrated by in vitro tests against various micro-organisms.
• Such a pharmaceutical composition will normally contain the pharmaceutically-acceptable carrier and a compound of formula II in a weight ratio in the range from 1:4 to 1:200.
• the antibacterial compounds of formula II, and the pharmaceutically-acceptable salts thereof are active in vivo versus a variety of Gram-positive microorganisms, e.g. Staphylococcus aureaus Streptococcus pyogenes , and also certain Gram-negative microorganisms, via the oral and parenteral routes of administration in animals, including man.
• Their in vivo activity is more limited than their in vitro activity as regards susceptible organisms, and it is determined by the usual procedure which comprises infecting mice of substantially uniform weight with the test organism and subsequently treating them orally or subcutaneously with the test compound. Extrapolation of such in vivo tests to support for human utility for macrolide compounds is likewise taught in U.S. Patent No. 4,518,590, cited above.

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  • 1992-04-06 CA CA002065218A patent/CA2065218A1/fr not_active Abandoned
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